The present invention relates, in general, to semiconductor devices, and more particularly, to a novel optical semiconductor device.
Previously, the semiconductor industry has produced optical modulators in the form of semiconductor devices that vary the amount of light passing through the modulator. Generally, the amount of light passing through the modulator is proportional to the voltage applied to the modulator. In the off state, the modulator absorbs incident light. As the applied voltage increases, the intensity of light transmitted through the modulator also increases. Typically, the transmitted light intensity varies gradually from the off state to the on state. Therefore, a large voltage change is generally required to switch these previous modulators from the off state all the way to the on state. For applications such as digital switching of optical signals, telecommunications, and other applications, the large voltage swings required by the previous optical modulators is a disadvantage.
Another disadvantage of the previous optical modulators is the operating wavelength or the wavelength of light that can be used with the modulators. As the applied voltage varies, the wavelength of light that has the highest transmission (lowest absorption) through the previous modulators also varies. Often, the wavelengths that can be transmitted with low absorption are wavelengths that are not entirely absorbed in the off state. Consequently, this wavelength variation with voltage typically results in a low contrast ratio between the off state and the on state of the previous modulators.
Accordingly, it is desirable to have an optical modulator that has a sharp transition from the off state to the on state, that requires a small voltage change to transition from the off state to the on state, and that has a high contrast ratio.